Damage From Coastal Flooding Could Soon Cost $1 Trillion A Year

Coastal flooding in cities around the world could cause damage
totaling $1 trillion annually by the year 2050 if no mitigating
steps are taken, new research suggests.

Almost all cities facing the worst damage are in Asia and North
America, the study showed. Three American cities — New York, New
Orleans and Miami — are at particularly high risk of damage,
according to the study, published today (Aug. 18) in the journal
Nature Climate Change.

"If we did nothing about the risk, the flood damages in coastal cities would grow to
huge amounts. So that's really not an option," said study
co-author Robert Nicholls, a coastal engineering professor at the
University of Southampton in England.

Damaging storms

Climate change models generally predict that storms will grow
more frequent and fierce over the next several decades. We may
already be seeing its impact: Many scientists believe that
climate change worsened the toll of Hurricane Sandy. [How Weird!: 7 Rare Weather Events]

After Hurricane Katrina ravaged the Gulf Coast in 2005, Nicholls
and his colleagues realized that scientists had little idea which
cities around the world were most vulnerable to flooding.

So the team compiled data on 136 coastal cities with more than 1
million residents, looking at the elevation of the cities, the
population distribution and the types of flood protection they had, such as levees or
storm-surge barriers.

They then combined that data with forecasts of sea level rise,
ground sinking due to groundwater depletion, as well as
population growth projections and economic forecasts of gross
domestic product (GDP). From there, they used the depth of water
flooding a city to estimate the cost of the damage.

U.S. Geological
Survey

Two vulnerable continents

The researchers found that in both their best- and worst-case
projections of sea level rise, the yearly global cost reached
higher than $1 trillion. The most vulnerable city was Guangzhou,
China, followed by Mumbai and Kolkata in India, Guayaquil,
Ecuador and Shenzen, China. Almost all cities at the highest risk
of flooding damage were in North America or Asia. [See The 20 Cities Most Vulnerable to Flooding]

If cities take steps to prevent damage — by increasing the height
of levees, erecting storm surge barriers, making buildings
flood-resistant or converting flood-prone, low-lying areas to
parks or football fields — the cost of the damage could be
brought down to about $50 billion annually.